The present invention relates to a liquid crystal display device and, more particularly, to a liquid crystal display device in which an illumination light source and a touch panel are stacked on a reflection type of liquid crystal panel which modulates light incident from its display-surface side and allows the modulated light to exit toward the display-surface side.
In recent years, so-called liquid crystal display devices using liquid crystal panels have been widely used as display devices which serve as monitors for image reproducing apparatus or various information terminals.
In general, such a liquid crystal display device uses a passive matrix type of liquid crystal panel which is known as an STN type, or an active matrix type of liquid crystal panel using non-linear devices such as TFTS.
These types of liquid crystal panel are not of the self light emitting type, and so they require an illumination light source to form a visible image formed on the liquid crystal panel. Liquid crystal panels are divided into a transmission type and a reflection type. In monitors for information terminals, the transmission type of liquid crystal panel is widely used for the purpose of high-luminance and high-contrast display, and for this purpose a backlighting illumination light source (hereinafter referred to as a backlight) is installed on the back of the liquid crystal panel, and a visible image is formed by modulating light from this backlight to form an image on the liquid crystal panel.
FIG. 10 is a cross-sectional view illustrating an example of a conventional liquid crystal display device provided with a transmission type of liquid crystal panel and a backlighting illumination device, i.e., a so-called backlight. The conventional liquid crystal display device has a backlight stacked on the back of the transmission type of liquid crystal panel, and is constructed to modulate, with an image formed on the liquid crystal panel, illumination light which is emitted from the backlight and which passes through the liquid crystal panel. The modulated illumination light is caused to exit toward the obverse side of the liquid crystal panel, thereby making the image visible.
On the other hand, a so-called touch panel may be stacked on the display-surface side of such a liquid crystal display device so that information can be externally inputted from the display surface of the liquid crystal panel.
Specifically, this kind of liquid crystal display device is constructed in the following manner, as seen in FIG. 10. In a liquid crystal panel 1, a liquid crystal layer is clamped between two transparent substrates 1A and 1B, and polarizers 1C are respectively provided on the obverse-surface side and the back-surface side of the liquid crystal panel 1. An illumination light. source 3 is provided, which includes an approximately rectangular transparent light guide plate 2, a light source (a light source made of a cold cathode fluorescent tube, a light emitting diode or the like) 3A installed along one edge of the light guide plate 2, and a reflection sheet 3B, and this illumination light source 3 is provided on the back surface of the liquid crystal panel 1. Light from the illumination light source 3 is deflected toward the liquid crystal panel 1 at an intermediate position, while being propagated in the light guide plate 2, and illuminates the liquid crystal panel 1 from the back surface thereof A light scattering area 10 formed by dot printing or the like is provided on the back surface of the light guide plate 2.
Furthermore, a reflector 11 for totally reflecting light which has exited from the light guide plate 2 on the back-surface side thereof and for returning the light to the liquid crystal panel 1 is installed on the back side of the light guide plate 2.
Such a backlight is stacked on the liquid crystal panel 1 with a light quantity distribution correction member such as a scattering film 12 or a prism plate (not shown), being interposed therebetween, whereby a transmission type of liquid crystal display device is constructed.
The above-described liquid crystal panel is undesirably limited in reduction in power consumption because the two transparent substrates 1A and 1B are used and the backlight installed on the back surface of the lower transparent substrate 1B is normally on.
In addition, a semi-transmission type liquid crystal display device is known in which a lower substrate of a liquid crystal panel is formed as a semi-transmissive substrate so that light (external light) incident from the display side of the liquid crystal panel is normally reflected by the lower substrate and is made to exit toward a display surface; whereas, if the quantity of external light is insufficient, an illumination device installed on the back surface of the liquid crystal panel is turned on. However, this type of device has the disadvantage that an insufficient contrast is obtained.
On the other hand, in a reflection type of liquid crystal display device in which a lower substrate of a liquid crystal panel is formed as a reflector, or when a reflector is installed on the back side of the lower substrate, since external light incident from a display surface is approximately 100% reflected and used for display, the contrast limitation experienced with the above-described semi-transmission type of liquid crystal display device is not a problem at all in a bright environment. However, in an environment in which external light, is insufficient, the contrast is insufficient as well. An illumination device may be installed to solve this problem, but unlike the semi-transmission type of liquid crystal display device, an illumination device cannot be installed on the back surface of the liquid crystal panel in the reflection type of liquid crystal display device.
In recent years, there has been a liquid crystal display device in which a touch panel 4 is stacked on the display-surface side of the liquid crystal panel 1 so that information may be externally inputted directly from the display surface of the liquid crystal panel 1. In this kind of touch panel, a spacer is inserted between at least two sheets or substrates which respectively have transparent conductive films formed on their inner surfaces opposed to each other, and a two-dimensional position on the liquid crystal panel is inputted by applying pressure at the position to vary the space between the two sheets or substrates.
The above-described illumination device for a liquid crystal panel has an optimum construction as a device which illuminates a transmission or semi-transmission type of liquid crystal panel from the back surface thereof However, it is meaningless to apply the illumination device to a liquid crystal display device which uses a reflection type of liquid crystal panel positively utilizing external light in the above-described manner.
In the reflection type of liquid crystal display device, in order that light incident from the obverse-surface side be totally reflected and be again made to exit from the obverse-surface side, a reflector is provided on the back surface or a reflection layer is formed on the inner surface of a lower substrate of the two substrates which constitute the liquid crystal panel.
However, in the reflection type of liquid crystal display device which uses external light as illumination light, a display is difficult to identify in a dark environment in which the external light is insufficient.
If a touch panel for inputting information is stacked on the display surface of the liquid crystal panel, the quantity of transmitted light decreases and the screen of the liquid crystal panel becomes darker and darker.
Incidentally, Japanese Patent Application No. 351794/1997 describes an arrangement in which a touch panel for inputting information and an illumination device for a liquid crystal panel are formed integrally with each other. However, in the arrangement disclosed in Japanese Patent Application No. 351794/1997, since the surface of an illumination-and-touch panel on which a light guide is provided is not flat, the connection between electrodes of the touch panel is far from good. In addition, in the arrangement disclosed in Japanese Patent Application No. 351794/1997, the surface on which the light guide is provided needs to be formed into a staircase-like shape so that the light of a light source is guided to the liquid crystal panel, with the result that the surface on which the light guide is provided cannot be made flat.
One object of the present invention is to improve the coordinate recognition characteristics of an information input device (touch panel) which is provided on a liquid crystal panel.
Another object of the present invention is to provide a reflection or semi-transmission type of liquid crystal display device in which a touch panel is stacked on the display surface of its liquid crystal panel and its entire effective display area is uniformly illuminated by a front illumination system so that a high-quality image display can be obtained and the brightness of the screen can be improved.
The above objects are achieved by providing on a display-surface side of a reflection type of liquid crystal panel a touch panel made of a hard transparent lower substrate and a soft transparent upper substrate, providing a transparent insulation film on the lower substrate, and forming a transparent electrode on the transparent insulation film.
The above objects are achieved by a liquid crystal display device in which an illumination device made of a light guide plate and a light source and a touch panel are provided or integrated on a display-surface side of a reflection type of liquid crystal panel to uniformly illuminate its entire effective display area so that a high-quality image display can be obtained and the brightness of the screen can be improved.
Specifically, a liquid crystal display device according to the present invention comprises a liquid crystal display panel having a first surface for displaying an image and a second surface different from the first surface, and a position information input device provided on a first-surface side of the liquid crystal panel, wherein the position information input device is made of a first substrate and a second substrate, more easily deformable than the first substrate, a transparent insulation film is provided over a surface of the first substrate opposed to the second substrate, and a first transparent electrode is provided on the transparent insulation film.
Furthermore, in the liquid crystal display device, the first substrate of the position information input device is provided between the second substrate and the liquid crystal display panel.
Furthermore, in the liquid crystal display device, a second transparent electrode is provided over a surface of the second substrate opposed to the first substrate.
Furthermore, in the liquid crystal display device, a spacer made of an insulating material is provided between the first substrate and the second substrate.
Furthermore, in the liquid crystal display device, a recess portion is formed on the surface of the first substrate opposed to the second substrate, and the transparent insulation film covers the recess portion to reduce unevenness of the surface over which the transparent electrode is provided.
Furthermore, in the liquid crystal display device, a printed layer for partly reflecting light is formed on the surface of the first substrate opposed to the second substrate, and the transparent insulation film covers the printed layer to reduce unevenness of the surface over which the transparent electrode is provided.
Furthermore, in the liquid crystal display device, the first substrate and the second substrate are fixed to each other by double-sided adhesive tape.
A liquid crystal display device according to the present invention comprises a reflection type of liquid crystal display panel, an illumination device provided over a display surface of said reflection type of liquid crystal display panel, and an input device provided over said illumination device, wherein the input device is made of a first substrate which is hard and a second substrate which is soft and is superimposed on the first hard substrate, a second transparent electrode is provided over a surface of the second substrate opposed to the first substrate, a transparent insulation film is formed over the first substrate, and a first transparent electrode is formed over the transparent insulation film.
Furthermore, in the liquid crystal display device, the first transparent electrode is made of an integral electrical resistance film which flatly spreads over an entire coordinate input area, while the second transparent electrode is made of an integral electrical resistance film which flatly spreads over the entire coordinate input area.
Furthermore, in the liquid crystal display device, a line for electrically connecting the first transparent electrode and a corresponding terminal is provided at a periphery of the first transparent electrode over the first substrate, and a fixing member for fixing the first substrate and the second substrate to each other is provided in an area of the first substrate in which the line is provided.
Furthermore, in the liquid crystal display device, the first transparent electrode is made of a plurality of X electrodes arranged in a first direction, and the second transparent electrode is made of a plurality of Y electrodes arranged in a second direction.
Furthermore, in the liquid crystal display device, the liquid crystal panel has a plurality of display electrodes arranged in the first direction or the second direction, and the distance between adjacent ones of the X electrodes or the Y electrodes is made equal to the distance between adjacent ones of the display electrodes.
A liquid crystal display device according to the present invention comprises a reflection type of liquid crystal panel and a touch panel stacked on a display-surface side of the liquid crystal panel, for externally inputting information, wherein the touch panel includes a hard lower transparent substrate opposed to the liquid crystal panel, a soft upper substrate for externally inputting information, transparent electrodes formed over inner surfaces of the lower transparent substrate and the upper substrate, respectively, and a spacer which is clamped between the lower substrate and the upper substrate and isolates the transparent electrodes from each other with a predetermined spacing, a light source being installed along at least one edge of the lower substrate, a surface-treated surface being provided over a surface of the lower substrate which is closer to the transparent electrode, the surface-treated surface reflecting and scattering light from the light source toward the liquid crystal panel and allowing light reflected from the liquid crystal panel to exit toward the display-surface side, and a transparent insulation film being provided between the surface-treated surface and the transparent electrode.
Furthermore, in the liquid crystal display device, a plurality of microprisms are formed over the surface-treated surface of the lower substrate, the transparent insulation covering the microprisms and differing in refractive index from the lower substrate.
Furthermore, in the liquid crystal display device, the distance between adjacent ones of the microprisms which are on a side of the lower substrate which is close to the light source is larger than the distance between adjacent ones of the microprisms which are on a side of the lower substrate which is far from the light source.
Furthermore, in the liquid crystal display device, those microprisms which are on a side of the lower substrate which is close to the light source are smaller in size than the microprisms which are on a side of the lower substrate which is far from the light source.
Furthermore, in the liquid crystal display device, a plurality of printed patterns are flatly formed over the surface-treated surface of the lower substrate, and the transparent insulation film covers the printed patterns to make the surface over which the transparent electrode is provided substantially flat.
Furthermore, in the liquid crystal display device, the distance between adjacent ones of the printed patterns which are on a side of the lower substrate which is close to the light source is larger than the distance between adjacent ones of the printed patterns which are on a side of the lower substrate which is far from the light source.
Furthermore, in the liquid crystal display device, those printed patterns which are on a side of the lower substrate which is close to the light source are smaller in size than the printed patterns which are on a side of the lower substrate which is far from the light source.
A liquid crystal display device according to the present invention comprises a reflection type of liquid crystal panel, and a touch panel stacked on the liquid crystal panel, for externally inputting information to a display-surface side of the liquid crystal panel, and the touch panel includes a lower transparent substrate opposed to the liquid crystal panel, an upper substrate softer than the lower transparent substrate, transparent electrodes formed over inner surfaces of the touch panel, and a fixing member which secures the lower substrate and the upper substrate to each other with a predetermined spacing, a light source being installed along at least one edge of the lower substrate, a surface-treated surface being provided over a surface of the lower substrate which is closer to the transparent electrode, the surface-treated surface reflecting and scattering light from the light source toward the liquid crystal panel and allowing light reflected from the liquid crystal panel to exit toward the display-surface side, and a terminal which is electrically connected to the transparent electrode being provided on a side of the touch panel on which the light source is not provided.
In any of the above-described liquid crystal display devices according to the present invention, the coordinate recognition characteristics of the information input device (touch panel) provided on the liquid crystal panel are improved.
In addition, any of the above-described liquid crystal display devices according to the present invention can be applied, irrespective of the kind of liquid crystal panel (a passive matrix, active matrix and any other types of liquid crystal panels) and the screen size thereof, so that an image of good visibility which has high luminance and is uniform over its entire effective display area can be obtained even in an environment in which the external light is insufficient.
It is to be noted that the above-described illumination device need not normally use the light source, but may also be provided with a switch or the like which turns on or off the light source, as required, so as to make it possible to turn off the light source if the luminance of the external light is high or to turn on the light source, as required, if the external light has a low luminance.